Humeral joint replacement component

ABSTRACT

A humeral prosthetic head has a non-spherical articulation surface coupled with an intermediate component connecting the head and the humerus, the intermediate component connected to the epiphysis, metaphysis, or diaphysis, or to one or more additional components connected to the humerus. The intermediate portion provides for axial and angular offset of the head with respect to a connection to the humerus, using a curvilinear tapered engagement.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application61/238,429, filed Aug. 31, 2009.

FIELD OF INVENTION

The present invention relates to the field of joint replacement and/orresurfacing, and more particularly total shoulder arthroplasty orhemiarthroplasty using a stemmed or humeral resurfacing prosthetic.

BACKGROUND OF THE INVENTION

Normal shoulder kinematics allows for translational motion of thehumeral head within the glenoid particularly at the end ranges ofpassive motion. These translations can be several millimeters and arethought to be due to capsular tightening on the opposite side of thedirection of humeral head translation. Small amounts of translationalmotion also occur with active range of motion and are correlated withthe degree of mismatch in the radii of curvature between the humeralhead and glenoid. The native articular surface of the humeral head isnot spherical in shape. Nevertheless, it is believed the central portionof the native humeral head is spherical and its curvature then decreasesout toward the periphery. In fact, one study shows that the nativehumeral head of adults has a shape of a semi-ellipsoid with its anteriorto posterior radius of curvature being approximately 2-3 mm less thanits superior to inferior radius of curvature. See J. Iannotti, J.Gabriel, S. Schneck, B. Evans, and S. Misra, The Normal GlenohumeralRelationships, The Journal of Bone and Joint Surgery, Vol. 74-A, No. 4(April 1992). The effect of a semi-ellipsoid native humeral head shapeon the kinematics of the shoulder joint has not been well defined. Basedupon the kinematics of the knee and femoral condyle anatomy, it would besuspected that asymmetric radii of curvature would allow for roll ortranslational motion of one surface on the other. It has been my longstanding hypothesis that a semi-ellipsoid humeral prosthetic head designmay allow for humeral head translation on the glenoid. This conceptbecomes important in prosthetic arthroplasty because translationalmotion of the humeral head and mismatch of the radii of curvature playan important role in wear and loosening of the glenoid component as wellas the materials that can be used for a load bearing surface.

In conventional shoulder prosthetic designs, the humeral prosthetic headis spherical in shape and normal translational motion is allowed by alarger radius of curvature of the glenoid component. Although this willallow for translation before rim loading thereby decreasing the risk ofloosening, it also increases the stress per unit area increasing thewear potential. In addition mismatched radii of curvature prevent theuse of metal on metal or ceramic bearing surfaces and limits thematerials to metal on plastic. One concept to manage or address theissue for allowing for humeral head translation versus decreased surfacecontact area is the biconcave glenoid design with a spherical head inthe Bigliani Flatow shoulder. This design proposed to improve wearcharacteristics when there is perfect conformity with the arm through amid range of motion, when the radius of curvature of the center of theglenoid was equal to that of the spherical humeral head, yet allowingfor translation at the end ranges of motion when the radius of curvatureof the glenoid increased. With use of the shoulder it has been suspectedthat the subtle differences in the radii of curvature of the polyglenoid would be lost due to plastic deformation of the part resultingin a uniform radius.

A requirement of humeral prosthetic surgery and design is the need toprecisely place the prosthetic within the area defined by the humeralosteotomy and to reproduce the center of rotation of the normal nativehumeral head of a patient. When using a resurfacing component properplacement can be achieved by the surgical technique when choosing thesite for preparing the humeral head. For a stemmed arthroplasty, this isachieved by surgical technique as well as prosthetic design which mayrequire an eccentric taper. An eccentric taper on a spherical head canbe effective in placement of the humeral prosthetic head in the optimalposition within the plane of the humeral osteotomy by rotation of thehumeral prosthetic head.

The art described in this section is not intended to constitute anadmission that any patent, publication or other information referred toherein is “prior art” with respect to this invention, unlessspecifically designated as such. In addition, this section should not beconstrued to mean that a search has been made or that no other pertinentinformation as defined in 37 CFR §1.56(a) exists.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention, a humeral prostheticprovides a non-spherical humeral head, having the shape of an ellipsoid,defined as a superior to inferior (SI) radius of curvature being greaterthan an anterior to posterior (AP) radius of curvature. The ellipticalhead of the invention may replace the entire or a portion of the nativehumeral head. The articulating surface can be affixed to the humerus byused of a stemmed component which in turn is fixed to the metaphysealand/or diaphyseal part of the humeral shaft. The invention provideseither a humeral hemiarthroplasty (articulation with the native glenoid)or with articulation with a prosthetic glenoid component. The ratio ofmajor and minor curvature of the articulating surface is varied tosupply a spectrum of anatomic shapes and sizes of humeral headcomponents, for example in the form of a kit, which may be convenientlyavailable in an operating theatre.

A variety of related devices and methods have been disclosed by theinventor, for example as may be found in U.S. Patent Publications2010/0016975, 2009/0254188, 2009/0187193, 2008/0269906, 2008/0140209,2008/0065226, 2006/0149390, 2006/0074430, 2005/0143829, 2004/0193278,2004/0193276, 2004/0193275, 2004/0193175, 2004/0193168, 2003/0125809,2004/0210317, and U.S. Pat. Nos. 7,604,665; 7,527,631; 7,338,498;6,699,289; 7,431,736, the contents of each of which are incorporated byreference herein.

Positioning of the humeral head component onto the stem isadvantageously accomplished using an intermediate component that may beprovided in a a variety of embodiments, described further herein. Theintermediate piece is advantageously, but not necessarily, centeredwithin the elliptical humeral head. The intermediate piece allows forrotation within the elliptical head and allows the head component to bepositioned onto the humeral surface without changing the orientation ofthe SI and AP dimension of the head, with respect to the SI and APdimensions of the humeral osteotomy surface. The intermediate pieceadvantageously includes a locking mechanism, for example a standard orMorse taper.

The stem surface of the intermediate piece has a centered or eccentricmale or female Morse taper connection so that rotation of theintermediate piece between the head or between the stem will allow fortranslation of the humeral head segment within the plane of theintermediate piece, while maintaining the anatomic orientation of themajor and minor axis of curvature of the articular surface of theelliptical head.

The device advantageously contains a non spherical modular humeral headarticulation having the shape of an ellipsoid such that the superior toinferior radius of curvature is greater than the anterior to posteriorradius of curvature. Its central portion, typically two thirds inhumans, may be spherical or may have also have an elliptical shape.

The articulating component contacts the native glenoid, in ahemiarthroplasty, or with a glenoid component, in a total shoulderarthroplasty (TSA). With respect to a TSA, the glenoid component maycontain a radius of curvature that is equal to the radius of curvatureof the central portion of the humeral head or have an intentionallylarger radius of curvature of the humeral head.

After the native humeral head, or a portion thereof, is removed, theelliptical prosthetic humeral head can be placed onto a stem componentthat obtains its fixation within the metaphysis and/or diaphysis of thehumeral canal/shaft. The stem component can achieve fixation by pressfit, porous coated biologic fixation, cement fixation, or any othersuitable means. The stem component can be contained within themetaphysis only or within the metaphysis and diaphysis of the humerus.

As noted above, positioning of the elliptical prosthetic humeral head tothe stem is advantageously accomplished using an intermediate piecehaving several alternative embodiments, described herein.

In one embodiment, a spherical disc is centered within the ellipticalhead and can rotate within the outer elliptical shell. An outerdimension of the intermediate piece is a Morse taper that can be lockedwithin the outer articulating piece through impaction of the Morsetaper. The intermediate piece connects with the stem using a male orfemale, centered or eccentric, Morse taper on its stem side thatconnects to a corresponding female or male Morse taper on the proximalend of the stem. Eccentric tapers can be located in any of a variety oflocations that are offset from a central axis, and alternative piecesmay be made available at the time of surgery, to increase options forthe practitioner.

Rotation of the intermediate piece about the eccentric taper connectingthe intermediate piece with the stem will result in translation of theelliptical head within the plane of the intermediate piece, for examplethe humeral osteotomy surface, while allowing for the major and minoraxes (curvatures) of the elliptical head to remain positioned in thedesired anatomic orientation prescribed by the patients anatomy.

In another alternative, an intermediate piece design includes aconnection of the intermediate piece with a fourth element. Theintermediate piece has a female Morse taper (centered or eccentric) andthe proximal end of the stem also has a female Morse taper. Theintermediate piece and stem are connected by a fourth component having afixed angle (e.g. double male Morse taper) or a variable angle (e.g.ball taper male taper having its ball taper on either the stem orintermediate piece female taper).

In yet another embodiment of the invention, the intermediate piece ispositioned within the humeral metaphysis, below the surface of theosteotomy, and below the stem side of the elliptical humeralarticulating component. In this embodiment, the humeral stem is insertedsufficiently below the humeral osteotomy surface to allow for placementof the intermediate piece. The intermediate piece has a male Morse taperon the stem side and a male or female (centered or eccentric) Morsetaper on the humeral head side. The intermediate piece can rotate aboutthe stem before being locked in place. With an eccentric Morse taper onits humeral head side the articulating component can be translatedwithin the plane of the intermediate piece, that is, a planecorresponding to the osteotomy surface.

In a further embodiment, an intermediate piece connects to a stem asdescribed elsewhere, however the humeral head side of the intermediatepiece, and the elliptical humeral head component, has a female centeredor eccentric Morse taper. The intermediate and humeral articulatingcomponents are connected with a double male (fixed angle) or variableangle (ball) taper. The ball taper can be placed within the intermediateor the humeral head piece and provides variable angulation between theintermediate piece and the humeral head component.

An alternative embodiment provides an intermediate piece having a convexspherical shape that is placed within a large female Morse taper in theouter shell of the articular component. In this design the articularcomponent can be elliptical or spherical in shape. After angularpositioning of the articulating component, using the infinite variationpermitted within the range, within the intermediate piece, thecomponents are impacted thereby locking then in place. The intermediatepiece becomes contained within the central portion of the ellipticalhumeral head. The stem surface of the intermediate piece has female ormale centered or eccentric, Morse taper, and is connected to theproximal stem via corresponding male or female tapers, respectively.Both the stem and the stem side of the intermediate pieceadvantageously, for example, have a female Morse taper connecting eachmember with a double male Morse taper.

In a further embodiment, the intermediate piece is a dome shaped convexspherical design that is contained within a mated concave sphericalsurface within the humeral head, which has an elliptical articulatingsurface. The intermediate piece is rotatable around the sphericalsurface, yielding infinite variability within a range of angulations ofthe outer elliptical, or outer articulating, surface segment. Theintermediate convex surface is locked into a concave articulation with ascrew or other locking mechanism, as would be understood by one skilledin the art. The stem side of the intermediate piece advantageously has acentered or eccentric male or female Morse taper, that connects to acorresponding female or male Morse taper, on the proximal end of thestem. An alternative is a female Morse taper on both the stem side ofthe intermediate piece and the proximal end of the stem. A double Morsetaper connects to the intermediate part, and thus connects the attachedelliptical or spherical head onto the stem.

The articulations materials may be metallic, polymeric, ceramic,composite, or a combination of materials, as would be understood by oneskilled in the art, or may be constructed using materials that are notyet known.

In another embodiment of the invention, the elliptical humeral headshape is advantageously applied in a surface replacement procedure toreplace the humeral surface. The embodiment contemplates the use of anon-spherical humeral head articulation having the shape of anellipsoid, such that the superior to inferior radius of curvature isgreater than the anterior to posterior radius of curvature. The implantobtains its fixation from an interference fit of a back side of a porouscoated prosthetic, and a machined (reamed) convex surface of a remaininghumeral head. A small stem contained within the epiphyseal portion ofthe humeral head is an optional means of fixation. The stemmed portionof the articular shell can be modular, or may be fixed to theundersurface of the resurfacing prosthetic. This embodiment may beadvantageously used either as a humeral hemiarthroplasty (articulationwith the native glenoid) or with articulation with a prosthetic glenoidcomponent.

In accordance with one embodiment of the invention, a device forreplacing a portion of a bone joint, comprises a prosthetic headcomprising an articulation surface having a shape of a semi-ellipsoid,and a bottom surface, wherein the bottom surface includes a taperfeature for engagement with an engagement member connectable to thejoint, the engagement member connectable to the prosthetic head andoperable to maintain a proper orientation of the semi-ellipsoid shape ofthe articulation surface with respect to the joint.

In accordance with alternative embodiments relating thereto, the devicefurther includes; the engagement member; a bone connecting member, thebone connecting member connectable to a bone of the joint, and tapermeans for connecting the bone connecting member to the engagementmember; the taper means includes at least one taper recess disposed inthe engagement member; the taper means includes a taper surfaceextending from the bone contacting member, adapted to frictionallyengage the at least one taper recess disposed in the engagement member;the bone connecting member includes at least one taper recess, and thetaper means includes a double ended taper operative to frictionallyengage at least one of the at least one taper recesses in the bonecontacting member, and at least one of the at least one taper recessdisposed in the engagement member; the taper means includes a balltaper, at least one end having an axially curved surface, whereby theprosthetic head is connectable to the engagement member at an angle,using the ball taper; the prosthetic head is a humeral head; the jointis a shoulder, and wherein the engagement member is sized anddimensioned to be engageable to bone of a humerus; the joint is ashoulder, and wherein the engagement member is sized and dimensioned tobe engageable upon a cut surface of a bone of a humerus; the engagementmember is sized and dimensioned to connect to the epiphysis ormetaphysis of a bone adjacent to the joint; the engagement member isconfigured to connect to a prosthetic stem associated within thediaphysis of a bone adjacent to the joint; the engagement memberincludes a prosthetic stem insertable within the diaphysis of a boneadjacent to the joint; the engagement member is connectable to aprosthetic stem, the prosthetic stem connected to bone of the joint; andthe device further comprises an opposing prosthetic articulating surfacemateable with the articulating surface disposed on a first side of thearticulating member.

In a further embodiment of the invention, a device for replacing aportion of a shoulder joint, comprises: an articulating member includingan articulating surface disposed on a first side of the articulatingmember, the articulating surface having a superior/inferior dimensiongreater than an anterior/posterior dimension, a spherical chamber formedin a second side of the articulating member; an engagement member,connectable to a bone of the joint, and including a spherical protrusiondisposed upon a first side of the engagement member, the sphericalprotrusion sized to be inserted, at any of a plurality of angles, atleast partially within the spherical chamber, whereby when the sphericalsurfaces are mated, the engagement member is secured to the articulatingmember by a friction between the mating spherical surfaces; wherein whenthe engagement member is connected to the bone of the joint, and thespherical surfaces are mated at a therapeutically effective angle, thearticulating member is therapeutically secured to the bone of the joint.

Alternative embodiments relating thereto include the mating sphericalsurfaces are connected together using a fastener, after being mated at atherapeutically effective angle; and the device further comprises a boneconnecting member, the bone connecting member connectable to a bone ofthe joint, and machine taper means for connecting the bone connectingmember to the engagement member; the machine taper means includes a balltaper, at least one end having an axially curved surface, whereby thebone connecting member and the engagement member are connectable at anangle, using the ball taper.

In yet another embodiment of the invention, a method of replacing aportion of a joint of a patient, comprises: making an incision in thepatient and exposing an articulating surface of the joint; cutting boneof the joint to remove at least a portion of a native articulatingsurface, and to form a spherical shape; positioning a prostheticreplacement, at any of a plurality of angles, upon the spherical shapeof the cut bone, the prosthetic replacement having a first sideincluding a replacement articulating surface, the replacementarticulating surface having a superior/inferior dimension greater thanan anterior/posterior dimension, the prosthetic replacement furtherhaving a spherical chamber formed in a second side, the sphericalchamber sized and dimensioned to conform to the size and dimension ofthe spherical shape of the cut bone; inserting the cut bone of the jointinto the spherical chamber; and aligning the articulating surface of theprosthetic replacement with a mating articulating surface in the body,by changing a position of the cut bone within the spherical chamber;wherein the prosthetic replacement therapeutically replaces the removedportion of a native articulating surface.

Further embodiments relating thereto include the joint is a shoulder;wherein cut bone and the articulating surface are connected by meansselected from the group consisting of: press fit, porous coated biologicfixation, cement; and wherein the radius of the replacement articulatingsurface, and the radius of a mating articulating surface in the patient,are not the same.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and inventive aspects of the present invention will becomemore apparent upon reading the following detailed description, claims,and drawings, of which the following is a brief description:

FIG. 1 is a cross section side view of a humeral prosthetic head havingan articulation surface of a semi-ellipsoid, an intermediate component,and a prosthetic stem fixed within a humeral shaft shown in an assembledstate in accordance with the present invention;

FIG. 2 is an exploded side view of the head, the intermediate component,and the prosthetic stem fixed within a humeral shaft illustrated in FIG.1;

FIG. 3 is a normal view of the articulation surface of the headillustrated in FIG. 1;

FIG. 4 is a cross-section view of the superior to inferior mid-sectionof the head illustrated in FIG. 1;

FIG. 5 is a cross-section view of the anterior to posterior mid-sectionof the head illustrated in FIG. 1;

FIG. 6 is a normal view of the articulation surface of the headillustrated in FIG. 1 with the plane of the humeral osteotomy locatedbelow the articulation surface indicated;

FIG. 7 is a normal view of the bottom surface of the head and theintermediate component as illustrated in FIG. 1 in an assembled state;

FIG. 8 is an exploded cross-sectional side view of the head, theintermediate component, and a portion of the stem as illustrated in FIG.2;

FIG. 9 is an exploded cross-section side view of an embodiment of thehead, the intermediate component and a portion of the stem in accordancewith the present invention;

FIG. 10 is an exploded cross-section side view of an embodiment of theintermediate component, a double male taper and a portion of the stem inaccordance with the present invention;

FIG. 11 is an exploded cross-section side view of another embodiment ofthe head, the intermediate component and a portion of the stem inaccordance with the present invention;

FIG. 12 is a normal view of the bottom surface of the head and theintermediate component as illustrated in FIG. 11 in an assembled state;

FIG. 13 is a normal view of the bottom surface of the head and anotherembodiment of the intermediate component in an assembled state inaccordance with the present invention;

FIG. 14 is a cross section view of the superior to interior mid-sectionof the intermediate component as illustrated in FIG. 13;

FIG. 15 is an exploded cross-section side view of an embodiment of thehead, the intermediate component and a portion of the stem in accordancewith the present invention;

FIG. 16 is an exploded cross-section side view of another embodiment ofthe head, the intermediate component and a portion of the stem inaccordance with the present invention;

FIG. 17 is an exploded cross-section side view of yet another embodimentof the head, a double male taper and the intermediate component inaccordance with the present invention;

FIG. 18 is a cross section side view of the head, the intermediatecomponent, and the stem illustrated in FIG. 15 wherein the stem is fixedwithin a humeral shaft and shown in an assembled state;

FIG. 19 is a cross section side view of an embodiment of the head, theintermediate component, a male taper, and a portion of the stem inaccordance with the present invention;

FIGS. 19A and 19B depict ball tapers in accordance with the invention,interposable between components of the invention to permit a desiredangle between the components;

FIG. 19C illustrates a cross section of an embodiment of the invention,illustrating a means of securing adjacent components of the invention;

FIG. 20 is a normal view of the bottom surface of the head and theintermediate component as illustrated in FIG. 19 in an assembled state;

FIG. 21 is a cross section side view of an embodiment of the humeralprosthetic head component and a portion of the resurfaced naturalhumeral head in accordance with the present invention;

FIG. 21A is a cross section of the embodiment of FIG. 21, disposed upona humerus;

FIG. 22 a normal view of the bottom surface of the component asillustrated in FIG. 21;

FIG. 23 is a cross section of an alternative device in accordance withthe invention, having two intermediate portions; and

FIG. 23A is a cross section of another alternative device in accordancewith the invention, having an intermediate portion supported upon boneof the joint.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1-23A, the present invention provides a humeralprosthetic head 100 having an articulation surface 108 of asemi-ellipsoid that is designed to be in communication with anintermediate component 102. Intermediate component 102 serves as aninterface between head 100 and a prosthetic stem 104. Stem 104 is fixedwithin the metaphyseal and/or diaphyseal part of a humeral shaft 106.This fixation of stem 104 within humeral shaft 106 is achieved byart-disclosed means such as press fit, porous coated biologic fixation,cement fixation, combinations thereof, or other mechanisms. Intermediatecomponent 102 engages with both head 100 and stem 104 as shown in FIGS.1 and 18.

The stem 104 can be any art-disclosed prosthetic stem designed to beplaced in humeral shaft 106. Stem 104 can be a unitary structure asshown in FIGS. 1-2 and 18. Alternatively, stem 104 can be constructedout of modular components (not shown).

Referring to FIGS. 3-6, head 100 has articulation surface 108 of asemi-ellipsoid. Semi-ellipsoid is defined in this application as havinga central point (C) and a central portion 109 that is spherical with apredetermined radius of curvature 111 (“ROC”) but the superior to theinferior surface curvature length 110 (“SI dimensions”) of articulationsurface 108 is greater than anterior to posterior surface curvaturelength 112 (“AP dimensions”) resulting in a peripheral contour 116 ofarticulation surface 108 being elliptical in shape as shown in FIG. 3.Correspondingly, the superior (S) to the inferior (I) radius ofcurvature of articulation surface 108 is also greater than the anterior(A) to the posterior (P) radius of curvature. Central point (C) is wherethe x-axis (direction between anterior (A) to posterior (P), the y-axis(direction between superior (S) and interior (I)), and the z axis(direction between top (T) and bottom (B)) of the head 100 intercept.

Notwithstanding the above, it should be understood that the formation ofa humeral head with a predetermined curvature of substantialmathematical precision is not a requirement of the invention. Indeed,the human body itself is not, in many respects, mathematically perfect,the shoulder or hip joints being examples. Rather, curves notcorresponding to a mathematical formula, but generally conforming to anSI dimension greater than an AP dimension are deemed to fall within adefinition of ellipsoidal, for the purposes of the instant invention anddisclosure.

Semi-ellipsoidal, in the context of the invention, refers to theconfiguration of head 100, in that it forms about a half of a completeellipse, as defined herein. However, head 100 may form substantiallymore or less than one half of an ellipse, while conforming to theinvention.

In one embodiment, ROC 111 of central portion 109 is the same as radiusof curvature of the central portion of a patent's native glenoid or aprosthetic glenoid component. This matching of radii of curvaturebetween central portion 109 and the central portion of the nativeglenoid or prosthetic glenoid component will improve the wearcharacteristics of the native glenoid in the case of a hemiarthroplastyor replacement components in the case of a total shoulder arthroplasty.In addition, this design can allow for the use of metal on metal and/orceramic bearing surfaces in the case of total shoulder arthroplasty. Itis optional that ROC 111 is same as radius of curvature of the centralportion of a patent's native humeral head.

The SI dimension 110, AP dimension 112, ROC 111 and head height 113 ofhead 100 (as shown in FIGS. 4-5) vary to accommodate difference inpatient size and pathologic changes to the shoulder. Accordingly, aspectrum of anatomic shapes and sizes of head 100 should bemanufactured. Exemplary ranges for SI dimension 110 are from about 31 mmto about 62 mm, from about 35 mm to about 58 mm, from about 39 mm toabout 54 mm. Exemplary ranges for AP dimension 112 are from about 29 mmto about 58 mm, from about 33 mm to about 54 mm, and from about 37 mm toabout 50 mm. Exemplary ranges for ROC 111 are from about 16 mm to about36 mm, from about 18 mm to about 34 mm, from about 20 mm to about 30 mm.Exemplary ranges for head height 113 are from about 12 mm to 26 mm, fromabout 13 mm to about 22 mm, and from about 15 mm to about 23 mm. Theterm “about” as used in this application shall mean+/−5% of the statedvalue.

A humeral head component may be constructed, for example, using valuesderived as follows:

The ratio between SI dimension 110 and AP dimension 112 of articulationsurface 108 can also vary and is dependent upon size and shape of apatent's native humeral head. Exemplary ranges for this ratio are fromabout 0.99 to about 0.83, from about 0.98 to about 0.85, and from about0.97 to about 0.86.

An exemplary linear equation for the relationship between SI dimension110 (“a”) and AP dimension 112 (“b”) is: a=2.53+1.01(b). An exemplaryquadratic equation for the relationship between SI dimension 110 (“a”)and AP dimension 112 (“b”) is: a=2.48+1.01(b)−0.004(b−43.1)².

An exemplary linear equation for the relationship between ROC 111 (“d”)and SI dimension 110 (“a”) is: a=8.61+1.53(d). An exemplary quadraticequation for the relationship between ROC 111 (“d”) and SI dimension 110(“a”) is: a=8.39+1.55(d)−0.04(d−24.4)².

An exemplary linear equation for the relationship between ROC 111 (“d”)and AP dimension 112 (“b”) is: b=8.46+1.41(d). An exemplary quadraticequation for the relationship between ROC 111 (“d”) and AP dimension 112(“b”) is: b=8.46+1.42(d)−0.02(d−24.4)².

An exemplary linear equation for the relationship between head height113 (“c”) and ROC 111 (“d”) is: c=3.98+0.56(d). An exemplary quadraticequation for the relationship between head height 113 (“c”) and ROC 111(“d”) is: c=4.33+0.53(d)+0.06(d−24.4)².

The articulation surface 108 is constructed of materials such as metal,polymer, ceramic, or a combination thereof, including compositematerials. The orientation of articulation surface 108 respects thenative orientation of natural replaced humeral head's semi-ellipsoidshape. This means that SI dimension 110 aligns along the SI dimension ofthe cut surface of humeral shaft 106 and AP dimension 112 aligns alongthe AP dimension of the cut surface of humeral shaft 106. The cutsurface of the humeral shaft is shown as 115 on FIGS. 2 and 6 and isalso known as the plane of the humeral osteotomy. The plane of humeralosteotomy 115 is indicated in FIG. 6 as beneath articulation surface 108upon implantation.

Referring to FIGS. 7, 12 and 13, bottom surface 114 of head 100 opposesarticulation surface 108. Unlike conventional prosthetic humeral heads,the general outer shape of bottom surface 114 (also known as peripheralcontour 116) is not spherical but elliptical.

Referring to FIG. 6, osteotomy surface 115 is shown to be slightlysmaller in size than peripheral contour 116 (which is same as thegeneral outer shape of bottom surface 114) and illustrates that SIdimension and AP dimension of osteotomy surface 115 is aligned with theSI dimension and AP dimension of articulation surface 108 and bottomsurface 114. In another embodiment, humeral osteotomy surface 115 isequal in size to peripheral contour 116.

Referring to FIGS. 8-9, and 11, bottom surface 114 includes a taperfeature 118 designed to engage with intermediate component 102. Taperfeature 118 is a machine taper, having a shank that gradually tapersalong the entire length of the mating portions. An example is a Morsetaper, but other machine taper configurations are known. The machinetaper is characterized in a connection by friction between the taperedmating surfaces, as opposed to an interlocking or threaded engagement.Intermediate component 102 is generally a cylindrical disc centeredwithin head 100. Specifically, the x, y and z axis of head 100 arecollinear with the x, y, and z axis of intermediate component 102, asmay be seen in FIG. 7. As interpreted with respect to FIG. 3, the x axiscould be construed to be the A/P axis, they axis the S/I axis, and the zaxis extending from the centerline c. With respect to the symmetricallyround intermediate component 102, the x and y axes bisect the component,and the z axis extends from the center. This center location ofintermediate component 102 allows for rotation of intermediate component102 within head 100.

Referring to FIGS. 8-9, intermediate component 102 includes a headsurface 120, side surfaces 122 and a stem surface 124. Head surface 120and side surfaces 122 define or form a male taper. Referring to FIGS.1-2 and 8-9, taper feature 118 is a female taper formed from a portionof bottom surface 114 for receiving male taper (120, 122). Theengagement of taper feature 118 with male taper (120, 122) engages orcouples head 100 with intermediate component 102. Both head 100 andintermediate component 102 in this situation will be placed above theplane of humeral osteotomy 115 as shown in FIG. 2.

A taper is advantageous in that it allows the tapered components to beassembled and aligned without tools, and provides a sufficiently strongconnection to maintain a respective position while the assembledcomponents are trial fit within the body. Performing the trial fit wouldtypically exert substantial misalignment forces upon the components,which a properly formed taper can withstand. If an initial trial fit isunsatisfactory, the tapered joint may be undone, either by applying anincreased amount of force, or by inserting a tool through an accessport, such as the aperture of locking feature 211, shown in FIG. 19.Alternatives to a taper include welding, cement, bonding with a thirdmaterial, including screws or cements, or other methods known to oneskilled in the art.

Prior to separating a trial fit, it may be advantageous to mark either aformer position, or a desired position, to facilitate proper subsequentalignment. Once a satisfactory trial fit has been achieved, the tapermay be further secured by applying cement to joined surfaces, or throughthe use of locking feature 211, discussed further below, through the useof a set screw impinging on a side surface of the taper, or by othermeans known in the art for securing a taper.

Referring to FIGS. 8-9, 12, and 15-16, stem surface 124 includes a taperfeature 126 for engagement with a taper feature 128 of stem 104. InFIGS. 8, 12 and 15, taper feature 126 is a male taper formed by having aportion of stem surface 124 extends obtusely from intermediate component102. Taper feature 128 is a female taper formed from a portion of stem104 for receiving taper feature 126. The engagement of these taperfeatures (126, 128) engages or couples intermediate component 102 withstem 104. In an alternative embodiment and referring to FIGS. 9 and 16,taper feature 126 is a female taper and taper feature 128 is a maletaper. In another alternative embodiment and referring to FIG. 10, taperfeature 126 is a female taper, taper feature 128 is also a female taperand a double male taper 130 is provided for engagement with both ofthese taper features (126, 128) thereby allowing the coupling ofintermediate component 102 and stem 104.

Referring to FIGS. 1-2 and 7-10, taper feature 126 is eccentricallylocated in intermediate component 102 such that the x, y, and z axis oftaper feature 126 are not collinear with (but are radially offset from)the x, y, z axis of intermediate component 102. Rotation of intermediatecomponent 102 about this eccentric taper feature 126 connectingintermediate component 102 with stem 104 will result in translation ofhead 100 within the plane of intermediate component 102 as well as theplane of humeral osteotomy 115, while allowing for SI dimension 110 andAP dimension curvature 112 of head 100 to remain positioned in thedesired anatomic orientation prescribed by the patient's anatomy.

In another embodiment of the invention, and with reference to FIGS.11-12 and 15-17, taper feature 126 is centrally located in intermediatecomponent 102 such that the x, y, z axis of taper feature 126 arecollinear with the x, y, z axis of intermediate component 102. In yetanother embodiment and referring to FIGS. 13-14, stem surface 124 ofintermediate component 102 has multiple (i.e., 2 or more) taper features126 that are either centrally located, eccentrically located, or acombination thereof. These multiple taper features 126 are likely to befemale tapers. The eccentrically located taper feature 126 as shown inFIG. 13 is not shown in FIG. 14 because FIG. 14 is a cross section viewof the superior to interior mid-section of intermediate component 102and this eccentrically located taper feature 126 is not located in thissuperior to interior mid-section.

In the embodiments discussed above and shown in FIGS. 1-2, 8-9, and 11,head 100 and the portion of intermediate component 102 that are receivedinto head 100 are placed above the plane of humeral osteotomy 115,during implantation as shown in FIG. 1.

In yet another embodiment and referring to FIG. 15, head face 120includes a taper feature 132. Taper feature 132 is formed by having aportion of head surface 120 extend obtusely from intermediate component102. In this embodiment, taper feature 118 is a female taper formed froma portion of bottom surface 114 for receiving taper feature 132.Alternatively, taper feature 132 can be a female taper for receivingtaper feature 118 which is now a male taper as shown in FIG. 16. Inanother embodiment taper features 118 and 132 are both female tapersthat can receive a double male taper 134 as shown in FIG. 17. Taperfeature 132, regardless whether it is a male taper or a female taper,and depending upon a user's choice, can be placed either centrally oreccentrically in relation to intermediate component 102. It is alsowithin the scope of the present invention to have multiple taperfeatures 132, e.g. multiple female tapers or the like. The embodimentsdiscussed in this paragraph, and for example shown in FIGS. 15-17,provide engagement between head 100 and intermediate component 102,wherein intermediate component 102 is located below the plane of thehumeral osteotomy 115. An example of a location of intermediatecomponent 102 below the plane of the humeral osteotomy 115, in a bone,is shown in FIG. 18.

In another embodiment of the invention, and with reference to FIGS.19-20, head 200 has an articulation surface 202 and a bottom surface204, similar to articulation surface 108, and bottom surface 114,discussed above. Intermediate component 206 has a head surface 208having a convex semi-spherical shape that can be received by a femaletaper feature 210 formed from bottom surface 204. The female taperfeature 210 can have any art-disclosed shape that can receive headsurface 208. For example, female taper feature 210 can be a concavesemi-spherical surface, a concave cone shape, a conventional femaletaper shape, or the like. In the embodiment illustrated, female taperfeature 210 forms a chamber including opposed planar surfaces, whereinopposite sides are advantageously disposed at an angle relative to eachother, to form a taper. With impaction, intermediate component 206 andhead 200 locks in place. In particular, head 206 forms a curvilinearsurface, in the embodiment shown, a spherical surface, which engages theopposed planar surfaces of female taper feature 210. The curved surfacesof head 206 readily admit head 206 within female taper feature 210, atany of a plurality of angles, to an appropriate predetermined depth,after which the curvilinear and opposed planar surfaces are press fittogether. In one embodiment of the invention, an appropriate depth isassured by engagement of head 206 with an upper roof surface of femaletaper feature 210. Additional frictional securement of head 206 andfemale taper feature 210 is accomplished by an angular displacement ofthe opposed planar surfaces of female taper feature 210, visible in FIG.19. A locking feature 211 (e.g. a screw and an opening withinintermediate component 206 for placement of such a screw) is optionallyprovided and shown in FIG. 19 in order to further assist engagement ofhead 200 and intermediate component 206. A fastener, such as a screw,not shown, is advantageously passed through taper feature 214 to beinserted into head 200, to avoid disruption to articulating surface 202.

Another view of a fastening mechanism is illustrated in FIG. 19C, inwhich shaft 226 passes through intermediate component 206, in whichcountersunk portion 232 is disposed within head surface 208. A threadedbore 226, axially aligned with shaft 226, is disposed in intermediateportion 102A, and is adapted to receive a threaded fastener, not shown,which is passed through shaft 226. It should be understood, however,that other approaches for further fastening intermediate portions arepossible, as may be understood by one skilled in the art.

With further reference to FIGS. 19-20, intermediate component 206 iscentrally located in head 200 such that the x, y, z axis of intermediatecomponent 206 are collinear with the x, y, z axis of head 200. Stemsurface 212 of intermediate component 206 opposes head surface 208. Stemsurface 212 includes one or more taper feature(s) 214 for engagementwith a corresponding taper feature 216 located within stem 218. Taperfeature(s) 214 is same as taper feature(s) 126, and taper feature 216 isthe same as taper feature 128, both as discussed above. Accordingly, thevarious embodiments discussed above for taper features 126 and 128 alsoapply to taper features 214 and 216. For example, taper feature(s) 214can be (i) either centrally located within intermediate component 206,eccentrically located within intermediate component 206, or acombination thereof; and (ii) a female taper, a male taper or multiplefemale tapers. For example, with reference to FIG. 19, taper features214 and 216 are female tapers for receiving a double male taper 220.Referring to FIGS. 19-20, one of taper features 214 is centrally locatedwhile the one of taper features 214 is eccentrically located withinintermediate component 206.

It is within the scope of the present invention to use different typesof art-disclosed tapers for the taper features (118, 126, 128, 130, 132,134, 210, 214, 216, 220) such as Morse tapers, ball tapers, or the like.For example, the taper features shown as male tapers in FIGS. 8-11,15-17 and 19, can be replaced with ball tapers, and double male taperscan be double or single ball tapers. The ball taper(s) placed within theintermediate component 102 and/or the head 100 may provide variableangulations between intermediate component 102 and head 100.

Ball tapers in accordance with the invention are illustrated in FIGS.19A-19B, for example, in which ball taper 220A or 220B replaces doublemale taper 220 in FIG. 19. If ball taper 220A is used, a pivot axis iscloser to head 200 than if ball taper 200B is used, however with the useof the latter, a wider dispositional offset of head 200 is attainable.Of course, a ball taper may be used with any taper connection disclosedherein, including instances where there is only a single taperedsurface, such as for example, taper 132, or taper 126, both shown inFIG. 18, wherein the mating surface is curvilinear, or spherical, asshown in FIGS. 19A-B. In another alternative, a double ended taper isused, however both tapered portions contain a curvilinear or sphericalshape, enabling yet greater positional possibilities. A ball taper inaccordance with the invention may be further secured as describedelsewhere, herein, should that be therapeutically advantageous.

Referring now to FIGS. 21-22, the present invention also provides ahumeral prosthetic head component 300 for resurfacing arthroplasty.Component 300 has an articulation surface 302 of a semi-ellipsoid and abottom surface 303 having a concave spherical feature 304 for receivingthe resurfaced (e.g., machined, reamed or the like) convex humeralsurface 306 of the remaining natural humeral head 308. In oneembodiment, the radius of curvature of concave spherical surface 304matches the radius of curvature of the convex humeral surface 306.Articulation surface 302 has the same properties as discussed above forarticulation surface 108. In one embodiment, concave spherical feature304 is centrally located in component 300 such that the x, y, z axis ofconcave spherical feature 304 are collinear with the x, y, z axis ofcomponent 300. In another embodiment, the x, y, z axis of concavespherical feature 304 is collinear with the x, y, z axis of nativehumeral head 308. In yet another embodiment, the x, y, z axis of concavespherical feature 304 is collinear with both the x, y, z axis ofcomponent 300 and the x, y, z axis of native humeral head 308. Component300 is fixed onto head 308 via art-disclosed engagement means such aspressure fit of concave spherical feature 304 with humeral surface 306,porous coated biologic fixation, cement fixation, or a combinationthereof.

With further reference to FIGS. 21-22, a stem 310 is optionally providedto further assist with fixation of component 300 to humeral surface 306.Stem 310 can be formed as part of the unitary structure of component 300or as a modular component that can be attached, via means known to oneskilled in the art, to concave spherical feature 304, as shown in FIG.21.

Referring again to FIG. 19C, head component 300A includes anarticulation surface 302A and concave spherical feature 304A, havingfunctions similar to analogous elements of FIGS. 21-21A, however in theembodiment of FIG. 19C, mating spherical surfaces are shown, includingintermediate component 206A which forms a spherical protrusion, whichmay be disposed within head component 300A at any of a plurality ofangles, as best meets the needs of the patient. In this embodiment,however, stem 310 is not provided, head component 300A being retained bypressure from ligaments, a friction or press fit with intermediatecomponent 206A, adhesive, or other means such as would be understood byone skilled in the art.

FIG. 23 illustrates an alternative embodiment of the invention, in whichat least two intermediate components, in this embodiment intermediatecomponents 102 and 230, are interposed between prosthetic stem 104 andhead 200. Mating taper surfaces 126A and 128A connect prosthetic stem104 and second intermediate component 230. An advantage of thisembodiment is that prosthetic stem 104 may be retained within bone 106during revision surgery, and either or both of components 102, 230replaced. More particularly, a new attachment may be made in theepiphysis, metaphysis, or both, without disturbing the attachment withinthe diaphysis, which can be difficult to remove. Additionally, eithercomponent 102 or component 230 may be rotated to produce a desiredoffset for head 200, each component providing a different angular and oroffset disposition, or the effects of each combined, enabling additionaltherapeutic positioning possibilities.

The embodiment of FIG. 23 illustrates a further aspect of the invention;more particularly, the potential to secure an ellipsoidal head of theinvention in the epiphysis, metaphysis, or diaphysis. Given a patientphysiology of adequate strength and health, intermediate component 230,and prosthetic stem 104 may be eliminated, and intermediate component102 alone serve as a sole support for head 200. In this embodiment,intermediate component 102 is supported by adjacent bone, advantageouslycortical bone in the epiphysis and or metaphysis of the humerus.Similarly, intermediate component 230 may be secured within theepiphysis and or metaphysis, again, without the use of prosthetic stem104. In the latter configuration, intermediate component 102 may also besecured to bone, or may only be secured by a taper or other connectionto intermediate component 230.

While FIG. 23 illustrates intermediate components 102 and 230 disposedentirely within the humerus, either or both components may be supportedon a cut edge of the humerus, as shown in FIG. 23A. As shown,intermediate component 102 is sized to rest upon a cut edge of corticalbone, and may be fastened thereto using any known means, including orlimited to, optionally, a tapered connection to a second intermediatecomponent 230, the latter supported by prosthetic stem 104, and or anindependent connection to bone. Alternatively, where patient physiologypermits, a second intermediate component 230, as well as prosthetic stem104, may be omitted. Intermediate component 102 may additionally beprovided with a portion extending into the metaphysis, shaped and sizedto connect to bone using known means.

The embodiments of the present invention including the head (100, 200)and the intermediate component (102, 206) discussed above can be usedeither as a humeral hemiarthroplasty (articulation with the nativeglenoid) or with articulation with a prosthetic glenoid component (totalshoulder arthroplasty). Accordingly, the present invention includesmethods of using the head (100, 200) and the intermediate component(102, 206) in humeral hemiarthroplasty and total shoulder arthroplasty.

The methods of the present invention may be combined with certainart-disclosed methods for humeral hemiarthroplasty and/or total shoulderarthroplasty; however, at least head 100, 200 and intermediate component102, 206 would replace a conventional spherical prosthetic head andrelated interface. In total shoulder arthroplasty, the prostheticglenoid component may contain a radius of curvature that is equal to orgreater than ROC 111.

Similarly, the present invention includes methods of using component 300in resurfacing arthroplasty. The methods of the present invention may becombined with certain art-disclosed methods for resurfacingarthroplasty; however, at least component 300 would replace theconventional spherical humeral prosthetic head component used in priorart resurfacing arthroplasty.

While the invention has been shown and described in the context of theshoulder, it should be understood that some or all aspects of theinvention may be used in applications involving any joint in the body,including the fingers, hand, wrist, elbow, spine, hip, knee, ankle,foot, and toes.

The explanations and illustrations presented herein are intended toacquaint others skilled in the art with the invention, its principles,and its practical application. Those skilled in the art may adapt andapply the invention in its numerous forms, as may be best suited to therequirements of a particular use. Accordingly, the specific embodimentsof the present invention as set forth are not intended as beingexhaustive or limiting of the invention. The scope of the inventionshould, therefore, be determined not with reference to the abovedescription, but should instead be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

Unless mention was made above to the contrary, it should be noted thatall of the accompanying drawings are not to scale. A variety ofmodifications and variations are possible in light of the aboveteachings without departing from the scope and spirit of the invention.

All references cited herein are expressly incorporated by reference intheir entirety. There are many different features to the presentinvention and it is contemplated that these features may be usedtogether or separately. Thus, the invention should not be limited to anyparticular combination of features or to a particular application of theinvention. Further, it should be understood that variations andmodifications within the spirit and scope of the invention might occurto those skilled in the art to which the invention pertains.Accordingly, all expedient modifications readily attainable by oneversed in the art from the disclosure set forth herein that are withinthe scope and spirit of the present invention are to be included asfurther embodiments of the present invention.

1. A device for replacing a portion of a bone joint, comprising: aprosthetic head comprising an articulation surface having a shape of asemi-ellipsoid, and a bottom surface, wherein the bottom surfaceincludes a taper feature for engagement with an engagement memberconnectable to the joint, the engagement member connectable to saidprosthetic head and operable to maintain a proper orientation of saidsemi-ellipsoid shape of said articulation surface with respect to thejoint.
 2. The device of claim 1, further including the engagementmember.
 3. The device of claim 1, further comprising a bone connectingmember, said bone connecting member connectable to a bone of the joint,and taper means for connecting said bone connecting member to theengagement member.
 4. The device of claim 3, wherein said taper meansincludes at least one taper recess disposed in said engagement member.5. The device of claim 4, wherein said taper means includes a tapersurface extending from said bone contacting member, adapted tofrictionally engage said at least one taper recess disposed in saidengagement member.
 6. The device of claim 5, wherein said boneconnecting member includes at least one taper recess, and said tapermeans includes a double ended taper operative to frictionally engage atleast one of said at least one taper recesses in said bone contactingmember, and at least one of said at least one taper recess disposed insaid engagement member.
 7. The device of claim 2, wherein said tapermeans includes a ball taper, at least one end having an axially curvedsurface, whereby said prosthetic head is connectable to said engagementmember at an angle, using said ball taper.
 8. The device of claim 1,wherein said prosthetic head is a humeral head.
 9. The device of claim2, wherein the joint is a shoulder, and wherein said engagement memberis sized and dimensioned to be engageable to bone of a humerus.
 10. Thedevice of claim 2, wherein the joint is a shoulder, and wherein saidengagement member is sized and dimensioned to be engageable upon a cutsurface of a bone of a humerus.
 11. The device of claim 2, wherein saidengagement member is sized and dimensioned to connect to the epiphysisor metaphysis of a bone adjacent to the joint.
 12. The device of claim2, wherein said engagement member is configured to connect to aprosthetic stem associated within the diaphysis of a bone adjacent tothe joint.
 13. The device of claim 2, wherein said engagement memberincludes a prosthetic stem insertable within the diaphysis of a boneadjacent to the joint.
 14. The device of claim 2, wherein saidengagement member is connectable to a prosthetic stem, the prostheticstem connected to bone of the joint.
 15. The device of claim 1, furthercomprising an opposing prosthetic articulating surface mateable withsaid articulating surface disposed on a first side of said articulatingmember.
 16. A device for replacing a portion of a shoulder joint,comprising: an articulating member including an articulating surfacedisposed on a first side of said articulating member, said articulatingsurface having a superior/inferior dimension greater than ananterior/posterior dimension, a spherical chamber formed in a secondside of said articulating member; an engagement member, connectable to abone of the joint, and including a spherical protrusion disposed upon afirst side of said engagement member, said spherical protrusion sized tobe inserted, at any of a plurality of angles, at least partially withinsaid spherical chamber, whereby when said spherical surfaces are mated,said engagement member is secured to said articulating member by afriction between said mating spherical surfaces; wherein when saidengagement member is connected to the bone of the joint, and saidspherical surfaces are mated at a therapeutically effective angle, saidarticulating member is therapeutically secured to the bone of the joint.17. The device of claim 16, wherein said mating spherical surfaces areconnected together using a fastener, after being mated at atherapeutically effective angle.
 18. The device of claim 16, furthercomprising a bone connecting member, said bone connecting memberconnectable to a bone of the joint, and machine taper means forconnecting said bone connecting member to said engagement member. 19.The device of claim 18, wherein said machine taper means includes a balltaper, at least one end having an axially curved surface, whereby saidbone connecting member and said engagement member are connectable at anangle, using said ball taper.
 20. A method of replacing a portion of ajoint of a patient, comprising: making an incision in the patient andexposing an articulating surface of the joint; cutting bone of the jointto remove at least a portion of a native articulating surface, and toform a spherical shape; positioning a prosthetic replacement, at any ofa plurality of angles, upon said spherical shape of said cut bone, saidprosthetic replacement having a first side including a replacementarticulating surface, the replacement articulating surface having asuperior/inferior dimension greater than an anterior/posteriordimension, said prosthetic replacement further having a sphericalchamber formed in a second side, said spherical chamber sized anddimensioned to conform to the size and dimension of the spherical shapeof the cut bone; inserting the cut bone of the joint into said sphericalchamber; and aligning the articulating surface of said prostheticreplacement with a mating articulating surface in the body, by changinga position of said cut bone within said spherical chamber; wherein saidprosthetic replacement therapeutically replaces the removed portion of anative articulating surface.
 21. The method of claim 20, wherein saidjoint is a shoulder.
 22. The method of claim 20, wherein cut bone andsaid articulating surface are connected by means selected from the groupconsisting of: press fit, porous coated biologic fixation, cement. 23.The method of claim 20, wherein the radius of said replacementarticulating surface, and the radius of a mating articulating surface inthe patient, are not the same.